R. A. Daly — Problems of the Pacific Islands. 



181 



and sporadic coral and nullipore growth. We now see why 

 each normal atoll or barrier reef is like a crown, laid on the 

 rim of a wide, flat plateau. 



The Glacial-control theory demands that many banks lying 

 outside the coral seas and not affected by post-Glacial move- 

 ments of the earth's crust, should now be at depths nearly 

 equal to those in the wide reef lagoons. This expectation is 

 amply met by the facts of the admiralty charts. Further, a 

 platform, which extends from the coral-sea area into a region 

 where the ocean water is too cold for coral growth, should 

 show nearly the same depths both in the lagoon of the reef- 



Figs. 31-33. 



1 







31 



11 



1 



5.E. 



1 



N.N.W. 



30 33 29 35 41 9 42 



46 45 45 42 43 43 34 26 31 S 



■ 







32 











1 



N.N.W. 9 1321 33 39 43 46 40 41 9 43 20 10 41 44 41 34 10 9 S.S.E. 



BBHI 



33| 



III 



if Sea Miles 



Figs. 31-33. Sections of large banks. Water shown in solid black ; 

 rocks, including reefs and coral knolls, are lined. Depths in fathoms. Uni- 

 form scales ; vertical scale is seven times the horizontal. 



31. Western end of the Seychelles bank, Indian ocean. 



32. Macclesfield bank, China Sea, where rimless. 



33. Macclesfield bank, Bhowing the main reef and coral knolls of this 

 " drowned atoll." 



covered tract and in the coral-free tract. The Great Barrier of 

 Australia illustrates just such a case, for it seems to be a partial 

 veneer on the warmer part of the 2,000-mile continental shelf 

 of Australia. Figures 26 and 27 are cross-sections of the reef- 

 affected, northern part of the shelf. Figures 28 and 29 are 

 sections of the reefless part of the same great feature. Do they 

 not indicate that the reefs are, in truth, shallow veneers % 



Finally, some of the open-ocean banks, even in the coral 

 seas, are reefless. Examples are illustrated in the accompany- 

 ing chart of the Bassas de Pedro bank and its neighbors in the 

 Indian ocean (fig. 30). The main bank is seventy-five miles 

 long, and, as shown by the soundings, has no reef. The depth 

 on such flat banks varies from 150 to 300 feet, and they seem 

 to be the little modified platforms which were smoothed by 



